This invention relates to a toner evaluation method that evaluates fixation performance of toner used in electrophotography. This invention also relates to a toner cartridge and an image forming apparatus that use the toner positively evaluated by the above evaluation method.
Heretofore, a so-called pressing/heating fixation system has been adopted to fix toner transferred onto a recording material, like recording paper, in an image forming apparatus for electrophotography. In the pressing/heating fixation system, for example, the recording paper after the toner is transferred is held between a heating roller and a pressing roller both provided in a fixing unit. The toner is then pressed onto the surface of the paper and heated to be melted so as to be settled and solidified onto the recording paper.
However, the fixing unit adopting such a pressing/heating fixation system requires a great amount of power. There are cases in which 70% of the total power consumption is spent for fixation in recent image forming apparatus. Therefore, development of various toners has been undertaken, which are excellent in low temperature fixability and offset resistance.
For example, Unexamined Japanese Patent Publication No. 8-278657 discloses a method for obtaining a toner by using two types of waxes having specific properties. Also, Unexamined Japanese Patent Publication No. 2001-222138 discloses a method for producing a toner by mixing an amorphous polyester and a crystalline polyester at a predetermined ratio.